The invention relates to an apparatus for mechanically locking the end positions of movable point sections, with two adjusting rods, each of which is connected with one of the point sections and which are coupled mechanically with one another, with at least one locking tappet for locking the adjusting rods in each case in one of their end positions and a force limiting device, which cancels the locking, when the force, exerted by the point sections on the adjusting rods, exceeds a certain value. In particular, the invention relates to an apparatus for locking the points of streetcar rails.
In the case of point section devices, it is important that the movable point sections are held securely in their respective end position. When a vehicle runs over a facing point, that is, when the wheels of the rail-bounded vehicle first run on the free ends of the points, the one switch rail, the so-called closed switch rail, must lie tightly against the continuous rail, while the other switch rail, the so-called open switch rail, must be at a sufficient distance from the associated continuous rail, so that the wheels can safely pass through the shunt and the rail-bound vehicle is not damaged or derailed. On the other hand, when a certain force is exceeded, the points must be able to yield, so that the rails of the rail-bound vehicle can yield laterally, when the point is passed trailing and the rail is not in the correct position. In the case of points that can be forced, the points in such a case remain in the new position, in which they have been set, that is, the shunt is shifted by the wheels of the rail-bound vehicle.
Shunt-adjusting devices are known, for which the adjusting rods for adjusting the two points are uncoupled mechanically and actuated in each case directly by the driving mechanism of the adjusting device and locked by respective locking clamps (such as clamp point locks). The contacting switch rail is locked rigidly, for example, against a rigid rail, while the remote switch rail is held by the self-locking or fixable driving mechanism. This arrangement has the advantage that the contacting switch rail can be held in its end position with a force, which is significantly larger than that holding the remote switch rail. The relatively high cost of the construction is, however, a disadvantage. In addition, the driving mechanism cannot be changed over manually with an adjustment plate and, when the point is forced, the adjustment rods are separated from the driving mechanism, so that the driving mechanism must be actively tracked into the new shunt position, so that the points are ready to function once again.
From practical experience, an adjusting device of the type named above is known (Hanning & Kahl HW 60 AW adjusting device), for which the two adjusting rods are coupled mechanically. The housing of the adjusting device preferably is disposed centrally between the two points, and the mutually coaxial adjusting rods enter the housing from opposite sides. Within the housing, the adjusting rods are rigidly connected with one another by a connecting piece. The locking tappet is disposed pivotably at the connecting piece and acts, on the one hand, with a locking plate, coupled with the driving mechanism of the adjusting device, and, on the other, with the force limiting device, disposed in the housing. Due to the force limiting device, both switch rails are held in the respective end position with the same force. If this force is exceeded when the points are forced, the force limiting device yields, the lock is unlocked and the shunt is shifted into the new position, in which the locking is brought about once again with the help of the locking tappet.